1. Field of the Invention
This invention relates to improvements in a loom equipped with a harness leveling motion, and more particularly to the improvements to prevent formation of a weaving defect such as filling bar in a woven cloth while obtaining a high operational efficiency of the loom.
2. Description of the Prior Art
It is well known that looms are equipped with a leveling motion to level warp yarns generally at the level of a warp line. The leveling motion incorporated with a cam-operated type shedding motion is disclosed, for example, in Japanese Patent Publication No. 3-68136 and Japanese Patent Provisional Publication No. 5-78953. The former Publication describes a mechanism accomplishing the following process: Upon detecting a breakage of a warp yarn by a warp yarn dropper, the weaving operation of a loom is stopped, and simultaneously the leveling motion connected with a heald frame is operated in response to a signal representative of this warp yarn breakage detection thereby leveling the warp yarns at the level of the warp line. After reparing the warp yarn breakage, the leveling motion is put into its inoperative condition to release its leveling action, and then the loom weaving operation is restarted.
The latter publication describes a mechanism accomplishing the following process: In the event that the weaving operation of a loom is stopped upon breakage of a warp yarn and failure in weft picking, the leveling motion is automatically operated to accomplish a so-called closed leveling in which all heald frames are leveled at an intermediate level of a shedding distance.
Thus, in the above-mentioned processes, the leveling motion is operated to change warp yarns from their open shed condition to their closed shed condition thereby preventing the warp yarns from being unduly stretched during the loom weaving operation stopping. This is because the cam-operated type shedding motion is such arranged that the amount (distance) of shedding is restricted by cams, so that the warp yarns cannot be readily put into their closed shed condition. It will be understood that leveling warp yarns can effectively prevent formation of filling bar in a woven cloth owing to the unduly stretched warp yarns under a long stopping time of loom weaving operation.
In recent years, it has been proposed that when a failure in were picking occurs in a loom, the weaving operation of the loom is stopped, and then a faulty weft yarn removing device is operated to automatically remove the faulty weft yarn from a woven cloth; and thereafter the loom weaving operation is automatically restarted. This is disclosed, for example, in Japanese Patent Provisional Publication No. 4-257348. In case of using the cam-operated type shedding motion on the premise that an automatic restarting of the loom weaving operation is made, when the failure in weft picking occurs, the faulty weft yarn removing device is first operated to automatically remove the faulty weft yarn from the were yarn path. Completion of this automatic faulty weft yarn removing operation provides no problem. However, if this faulty weft yarn removing operation fails, the faulty were yarn must be manually removed by an operator under a condition where the faulty weft yarn is exposed at the cloth fell while the warp yarns are kept in the maximum open shed state in order to facilitate the operator's manual removal operation. Usually a long time is required until the operator comes to the loom and completes a removing and repairing operation for the faulty weft yarn. During this long time, the warp yarns are being kept stretched thereby causing a filling bar in the woven cloth at the restarting of the loom weaving operation.